Method of coating copper and its alloys



Patented Feb. 10, 1942 UNITED STATES PATENT OFFICE- METHOD OF COATING COPPER AND ITS ALLOYS Herman J. Lodeesen, Royal Oak, Mich., assignor to Parker Rust Proof Company, Detroit,

Mich.

No Drawing. Original application June 6, 1938,

Serial No. 212,209. Divided and this application September 28, 1940, Serial No. 358,837

Claims.

To 100 gallons of water, add- Pounds Manganese acid phosphate solution"- 40 Zinc carbonate 1.5 Hydrogen peroxide (30%) 2 problem for the reason that copper has a surface of such a nature that it prevents the proper ad hesion of paint to it. The peculiar characteristics of such a surface cannot be entirely overcome by any of the well-known cleaning methods so far evolved. The present invention discloses a new and improved process for preparing the surface of eopper and its alloys to receive a siccative coa In building up a coating solution, it has been found that the best results are obtained from the use of either zinc or manganese acid phosphate, although cadmium or magnesium acid phosphate may be employed. Copper, and an alloy such as brass, do not react the same insofar as their ability to take a coating is concerned. For example it has been found that a satisfactory solution for the coating of brass consists of a solution made up in the following manner:

To 100 gallons of water, add- Pounds Zinc dihydrogen phosphate 42 Ammonium persulfate 8 Time: 5 minutes at 200 F.

Other examples of solutions for coating brass are: v v

To 100 gallons of water, add- Pounds Manganese acid phosphate solution" 40 Zinc carbonate 1 Sodium nitrite 4 Time: minutes at 210 F. v

For better results, add nitrite continuously, due to its decomposition.

Sodium nitrite Time: 5 minutes at 200 F.

' point of economy, although stronger solutions are just as effective. A treatment of one minute in The. above mentioned manganese acid phosphate" solution is made u by adding to 100 gallons of water gallons of losphorlc acid and 35 lbs. of normal manganese pliosp ate.

The pieces to be treated may be submerged in the above outlined solutions, or the'solutions may be sprayed onto the work. If the article to be coated contains heavy grease the same should first be removed by any of the well-known grease solvents. If no such grease is present a hot water immersion or spray for approximately two minutes has been found very beneficial,

The increase of zinc content in the above soluticns by adding a soluble zinc'salt, such as zinc sulphate or zinc nitrate, improves the coating a great deal.

All of the above mentioned baths dissolve considerable copper from the work being treated which copper is retained in the solution to some extent and apparently has some balancing effect to produce a better coating as the solution becomes aged.

A copper compound, such as copper carbonate or copper sulfate may be added before processing, when desired.

The following accelerating metals may also be used: antimony, nickel and silver.

With any .of the above solutions the work may be immersed therein or if more convenient the solutions may be sprayed onto the work by means of any of the well-known spraying equipments.

It has been further discovered that when the coatings produced in accordance with this invention are subject to a final rinse in a solution of the kind described below, the corrosion resistance is still further enhanced. For this purpose a dilute solution of chromic acid, phosphoric acid, oxalic acid or a salt of iron, chromium or aluminum may be used, such as aluminum nitrate or sulfate, ferrous sulfate, ferric nitrate and chromic sulfate or nitrate. A particular advantage derived from the use of one of these final rinses is that subsequent paint blistering is reduced to a minimum. The solutions may be used from F. to F.-

From '7 to 21 ounces of the acid or salt perlOO gallons is the preferred strength from the standthese solutions is sufficient.

There has been disclosed a new and improved process for coating copper and its alloys whereby a metallic surface is converted to a nonmetallic phosphate coating which in turn may be readily painted. Objects of copper, brass, or the like, have presented a problem for years on account of their tendency to tarnish when exposed to atmospheric conditions for any great length of time and the impossibility to make paint adhere to their surfaces. After the object has been treated as disclosed in the present application, the article being treated may be painted any desirable color, and the paint, enamel, or the like, forms an additional protective coating for the metal.

What I claim is:

l. A process for producing corrosion retarding coatings on articles of copper and its alloys which comprises subjecting th surface thereof to the action of a solution containing an acid phosphate selected from the group consisting of zinc, manganese, cadmium and magnesium and an oxidizing agent selected from the group consisting of persulphates, permanganates, iodates, nitrites and peroxides.

2. A process for producing corrosion retarding coatings on articles of copper and its alloys which comprises subjecting the surface thereof to the action of a solution containing an acid phosphate selected from the group consisting of zinc, manganese, cadmium and magnesium and an oxidizing agent selected from the group consisting of persulphates, permanganates, iodates, nitrites and peroxides, and thereafter subjecting the articles to a rinse in a solution containing an acid selected from the group consisting of chromic acid, phosphoric acid and oxalic acid.

3. A process for producing corrosion retarding coatings on articles of copper and its alloys, which comprises subjecting the surface thereof to the a c t 1on of a solution containing an acid phosphate selected from the group consisting of zinc, manganese, cadmium and magnesium and an oxidizing agent selected from the group consisting of persulphates, permanganates, iodates, nitrites and peroxides, and thereafter subjecting the articles to a rinse in a solution containing a salt selected from the group consisting of iron, chromium and aluminum.

4. An object of copper and its alloys having on the surface thereof an integral coating having the composition resulting from treating the copper metal object with a solution containingan acid phosphate selected from the group consisting of zinc, manganese, cadmium and magnesium, and an oxidizing agent selected from the 7 duction of corrosion retarding coatings on articles of copper and its alloys comprising an acid phosphate selected from the group consisting of zinc, manganese, cadmium and magnesium, and an oxidizing agent selected from the group consisting of persulphates, permanganates, iodates, nitrites and peroxides.

6. An object of copper and its alloys having on the surface thereof an integral coating resulting from treating the object with a solution containing an acid phosphate selected from the group consisting of zinc, manganese, cadmium and magnesium, and an oxidizing agent selected from the group consisting of persulphates, permanganates. iodates, nitrites and peroxides and thereafter rinsed with a solution containing hexavalent chromium.

'7. A process for producing corrosion retarding coatings on articles of copper and its alloys which comprises subjecting the surface thereof to the action of a solution containing zinc dihydrogen phosphate and an oxidizing agent selected from the group consisting of persulphates, permanganates, iodates, nitrites and peroxides.

8. A process for producing corrosion retarding coatings on articles of copper and its alloys which comprises subjecting the surface thereof to the action of a solution containing zinc dihydrogen phosphate and an oxidizing agent selected from the group consisting of persulphates, permanganates, iodates, nitrites and peroxides and rinsing the coated surface with a solution containing hexavalent chromium.

9. An object of copper and its alloys having on the surface thereof an integral coating having the composition resulting from treating the object with a solution containing zinc dihydrogen phosphate, and an oxidizing agent selected from the group consisting of persulphates, permanganates, iodates, nitrites and peroxides.

10. An object of copper and its alloys having 

